the development of water-power for that purpose. The National Academy of Sciences had in April of that year offered its services in scientific matters; and a little later the Secretary of War requested the Academy to appoint a committee to advise him as to the best method to be followed in the manufacture of nitric acid by a process not involving dependence upon a foreign source of supply." A committee was formed consisting of leading chemists and engineers; and this committee rendered on June 2, 1916 a preliminary report urging that in view of the unavoidable delays in the construction of adequate fixation-plants, a large supply of Chile saltpeter be imported as rapidly as possible and stored against an emergency; and that efforts be made to stimulate the introduction of byproduct coke ovens for the production of ammonia and hydrocarbons. The committee then proceeded to make an exhaustive study of the different problems of nitrogen-fixation under American conditions, and in January, 1917, rendered to the Secretary a full report. In this report the previous recommendations were renewed; and in addition the immediate construction of a plant for the oxidation of coke-oven ammonia to nitric acid and of a cyanamide-process plant for the fixation of nitrogen was recommended, the latter plant to be operated temporarily with newly developed steam power or with existing power purchased from private companies. The cyanamide process was recommended; for it was evident that sufficient power could not be secured for the operation of a large arc-process plant, and no information was available that would make possible the proper construction and operation of the German synthetic process. In the meantime the Chief Chemist of the Bureau of Mines had been sent abroad by the War Department to study foreign developments of nitrogenfixation, on which he presented a report in January, 1917.

This Academy Committee was later replaced by the official Nitrate Commission of the War Department with a personnel that included several members of the original committee and a number of prominent government representatives; and the

Commission acted in an advisory capacity to the Secretary throughout the war.

During the summer of 1917 a Nitrate Division was organized in the Ordnance Department; and contracts were made for the construction of two fixation-plants. The first one of these arranged for was a synthetic-process plant to be built at Sheffield, Alabama, by the Government with the coöperation of the General Chemical Company, employing the recently disclosed process of that company. It was to have a capacity of 20,000 tons of ammonium nitrate a year. This plant was constructed during the following year; and one of the three units was completed before the armistice was signed. Its continuous operation was, however, prevented by difficulties which had not then been overcome.

The second fixation plant was built at Muscle Shoals, Ala"bama, for the government by the American Cyanamid Company. It is the largest, and doubtless the most perfect, cyanamide-process plant ever constructed. It is designed for the production of ammonium nitrate, and has a capacity of 110,000 tons of that material per year. It was already partly in operation at the time of the armistice, but has since been shut down, pending decision as to the practicability of manufacturing nitrogen-products for fertilizer use upon a paying basis.

As the American Army grew in size, with still larger increases in prospect, the need of ammonium nitrate became still more pressing; and the construction of two new cyanamideprocess plants, each with a capacity of 55,000 tons of ammonium nitrate per year, was begun in the summer of 1918. These were located near Toledo and near Cincinnati, Ohio, where surplus municipal power was available. The construction was suspended, and the structures were salvaged when the armistice was declared.

As in many other fields involving the applications of science, the war demands have given a great stimulus to the develop

ment of the art of nitrogen fixation,- an art which, by furnishing cheaper fertilizer and thereby increasing the crop-production of the world, is bound to contribute greatly to the welfare of mankind. From the beginning of the war, the governments of England, France, and the United States, as well as many of the large chemical companies of those countries, actively prosecuted investigation in this field. When the Nitrate Division of our Ordnance Department was formed, it established a Research Section, and this actively assisted industrial companies and inventors in the development of their processes. And, in coöperation with the Nitrate Investigations Committee of the National Research Council, it initiated and prosecuted researches of its own, in its laboratories at the Nitrate Plant at Sheffield, in those of the bureau of Chemistry and Bureau of Soils at Arlington, and at the Geophysical Laboratory of the Carnegie Institution, which during the latter period of the war liberally placed its facilities and assigned some of its staff to this work,

It is a subject for congratulation that provision has been made by the Government for the continuation of researches upon nitrogen fixation under most favorable conditions. The excellent laboratories at the American University previously used by the Chemical Warfare Service are now utilized for this purpose, funds enough to enable the work to be effectively prosecuted for some time are available, and the investigations are under the competent direction of some of our best research chemists, who will attack the difficult problems involved in a fundamental way.

In conclusion, the hope may be expressed that this brief story of nitrogen fixation in its war relations may contribute to the purposes of this volume by showing the vital dependence of military operations upon the applications of science, and the reactions of war experiences on the development of science itself.

IX

THE PRODUCTION OF EXPLOSIVES

CHARLES E. MUNROE

INCE the introduction of gunpowder into use it has been

SINCE

quite generally recognized that explosives are essential in the carrying on of war, and it is expected that large quantities of them will be consumed in warfare. It is not as generally recognized that explosives are equally essential for use in industry and that the demands of our modern civilization for coal and many of the ores, and for the carrying out of engineering and a variety of other operations, cannot be met except through the use of enormous quantities of these reservoirs of concentrated energy. An inspection of our census statistics will show a constantly increasing production of explosives until 1909, when there were manufactured in the United States 244,622 tons of explosives in one year, of which less than one-half of one per cent. were designated for military uses. It is believed that the annual production in subsequent years, except that of 1914, was greater than the above but no U. S. Census statistics have been taken except those for 1914 when production of all kinds was lessened during the last six months. (All civilized countries have been engaged in the manufacture of explosives, though none upon so extensive a scale as the United States, during the last half century.

For several hundred years after its introduction men depended upon potassium nitrate gunpowder alone to perform all the variety of duties demanded of explosives in peace or in war, and it early became the subject of scientific investigation and supervision; Tartaglia, Galileo, Newton, Huygens, and

many other mathematicians and physicists discussed its effects on projectiles; granulation was introduced in 1445; Benvenuto Cellini observed the necessity for adapting the grains to the gun, and devised the system of blending; Hawksbee, in 1702, measured the volume of gas resulting from a known volume of powder; Robins, and then Hutton, developed the ballistic pendulum; and Rumford measured the pressure produced by gunpowder in burning, all prior to the nineteenth century.

In connection with his duties in the office of the fermier général of France, Lavoisier was, in 1775, designated registeur des poudres, when he at once proceeded to install a laboratory at the Arsenal in Paris and to apply his chemical knowledge to improvements in the production of saltpeter and in the manufacture of gunpowder. Among his pupils was E. I. du Pont de Nemours, who spent some time in the royal powder mills at Essone, qualifying as a successor to Lavoisier as superintendent and who, on July 19, 1802, on the advice of Thomas Jefferson, began the gunpowder works on the Brandywine at Wilmington, Delaware, which have been continued to the present day.

The creation of this laboratory by Lavoisier may properly be taken as the beginning of precise chemical investigations of explosives, and his example was followed by many other chemists, among those investigating gunpowder being Berthollet, Gay Lussac, Violette, Chevreul, Bunsen and Schischkoff, Linck, Károyli, Noble and Abel, Hare and Debus.

Although picric acid had then been known and, to some extent, used as a bitter principle and coloring matter, and with metal-amines, styled fulminating silver, gold and the like, had been developed as interesting chemical material, the beginning of modern explosives dates from the discovery of mercury fulminate by Howard in 1800, and from the middle of the nineteenth century on followed the discovery of the nitric esters from starch, wood, cotton, glycerin, sugars and other alcohols, known as nitro starch, nitro lignin, nitro cellulose, nitro glycerin, and nitro sucrose; of diazo-bodies, and of hydronitrides;